Regioselective homogeneous hydrogenation of heteroaromatic nitrogen compounds by use of [RuH(CO)(NCMe)2(PPh3)2]BF4 as the precatalyst

Summary The complex [RuH(CO)(NCMe)₂(PPh₃)₂]BF₄ (1) is an efficient and regioselective catalyst precursor for the hydrogenation of polyaromatic nitrogen compounds such as quinoline (Q), isoquinoline (iQ), indole (ln), 5,6- and 7,8-benzoquinoline (BQ) and acridine (A) under relatively mild reaction conditions (125 °C, 4 atm H₂). The order of individual initial rates was: A > Q > 5,6-BQ > 7,8-BQ > ln > iQ, reflecting both steric and electronic effects. For the regioselective homogeneous hydrogenation of A to 9,10-dihydroacridine (DHA) catalysed by complex (1), a kinetic study was carried out; the experimentally determined rate law was r = k ₁ [Ru] [H₂]. These findings are consistent with a mechanism involving the hydrogenation of [RuH(CO)(A)(NCMe)(PPh₃)₂]BF₄ to yield DHA and the unsaturated species [RuH(CO)(NCMe)(PPh₃)₂]BF₄ in the rate-determining step.     

Homogeneous pyrolysis kinetics of ethyl 3-hydroxy-3-methylbutanoate in the gas phase

The pyrolysis kinetics of ethyl 3-hydroxy-3-methylbutanoate have been examined over the temperature range of 286–330°C and pressure range of 29–108 Torr. In a seasoned vessel and in the presence of the free radical inhibitor cyclohexene or toluene the reaction is homogeneous, unimolecular and obeys a first-order rate law. The elimination products are mainly acetone and ethyl acetate, and very small amounts of ethyl 3-butenoate, acetic acid, ethylene and H₂O. The rate coefficient is expressed by the following equation: log k₁(s^–1)=(12.39±0.46)–(174.5±5.2) kJ mol^–1 (2.303RT)^–1. The mechanism appears to proceed via a six-membered cyclic transition state, where polarization of the (CH₃)C(OH)^+...-CH₂COOCH₂CH₃ bond is rate determining.     

Quantification of arecoline (areca nut alkaloid) in neonatal biological matrices by high-performance liquid chromatography/electrospray quadrupole mass spectrometry

A high-performance liquid chromatography (HPLC) method with mass spectrometric detection is described for determination of arecoline in newborn meconium, urine and cord serum, using pilocarpine as internal standard. The analytes were extracted from neonatal biological matrices with chloroform/isopropanol (95:5, v/v) at alkaline pH. Extracts were analyzed by HPLC coupled to an electrospray (ESI) interface and a quadrupole mass spectrometer. Chromatography was performed on a C(8) reversed-phase column using 10 mM ammonium acetate (pH 4.3)/acetonitrile (90:10, v/v) as mobile phase. The mass spectrometer was operated in selected ion monitoring mode. The method was validated over the concentration range 0.005-1.00 micro g/g meconium, 0.004-1.00 micro g/mL cord serum and 0.001-1.00 micro /mL urine. Mean recoveries ranged between 86.5 and 90.7% for arecoline in the different biological matrices, with precision always better than 10%. The quantification limits of arecoline were 0.005 micro g/g meconium, 0.004 micro g/mL cord serum, and 0.001 micro g/mL urine. The method was applied to the analysis of neonatal biological matrices to assess eventual fetal exposition to arecoline. Two newborns from Asian mothers who declared areca nut consumption presented arecoline in meconium with concentrations in the range 0.006-0.008 micro g/g; also the urine from one neonate tested positive for the drug.     

Iridium complexes of the doubly cyclometalated NHC ligand IMes'

Two consecutive C-H bond activations at the coordination sphere of Ir transform the commonly employed NHC ligand IMes into the new κ(3)-C fac-coordinating ligand IMes'. The preparation and structure of Ir(III) complexes featuring this ligand together with selected reactions toward small molecules that illustrate their reactivity keys are described.     

Galois Connections Between Lattices of Preradicals Induced by Adjoint Pairs Between Categories of Modules

We extend the result which establishes that every equivalence between categories of modules induces an isomorphism between the corresponding lattices of preradicals, proving that every adjoint pair between categories of modules induces a Galois connection between the corresponding lattices of preradicals. We prove some general properties of this Galois connection. In particular, given an ideal I of a ring R we study the Galois connection induced by the natural projection R→R/I and we prove that it yields a partition of R-pr into intervals, which are described. We study this partition in the case of the ring \(\mathbb {Z}\) and ideals \(p^{n}\mathbb {Z}\) and use it to locate the idempotent radicals on abelian groups.     

Evaluation of crude oil oxidation by accelerating rate calorimetry

Accelerating rate calorimetry has been used to study the thermal behavior of the combustion reactions that occur during the in situ combustion process and to estimate key parameters for the numerical simulation studies. This work reports the results from a study on the combustion reactions of heavy oil based on experimental tests using an accelerating rate calorimeter. The temperature settings covered a ramped ranging from 50 to 550 °C. The pressure was kept constant at 20 and 40 bar, and the air flow rates were tested for values of 90 and 120 mL min^?1. An experimental design was built to provide the effects of pressure, air inflow, and oil mass on the main kinetic parameters. Activation energy was 0.6–64 × 10³ kJ mol^?1, with higher variation in Test-1. LTO region was represented by just one reaction and its activation energy was ~10² kJ mol^?1 across every tests. Process variables were found to affect the exothermal temperature interval, the activation energy, and the order of reaction. Effects of variables on the kinetic parameters were found to be dependent on specific reaction temperature range, being more pronounced in the range of higher temperatures.     

Addition of Hydrogen Peroxide to Groundwater with Natural Iron Induces Water Disinfection by Photo‐Fenton at Circumneutral pH and other Photochemical Events

Samples of natural groundwater (with low turbidity, neutral pH and 0.3 mg L^?1 iron concentration) inoculated with Escherichia coli K‐12 were exposed to simulated solar light both in the presence and in the absence 10 mg L^?1 of H₂O_2. Results demonstrated that the viability of E. coli (by DVC–FISH) was grounded to zero after 360 min of irradiation. This abatement could be caused by the oxidative stress induced by radicals or another photo‐induced reactive oxygen species. Two 2³ factorial experimental designs enabled the evaluation of the effects of chemical factors on the inactivation of E. coli. The first experimental design considered the pH, iron and H₂O₂, while the second evaluated the ions fluoride, carbonate and phosphate found in groundwater. pH was found to play a key role in the inactivation of E. coli. The best reduction in viability was obtained at the lower pH (6.75), while a nonsignificant effect was observed when iron or H₂O₂ concentrations were raised. At higher concentrations, anions, such as carbonate and phosphate, negatively affected the E. coli abatement. However, a higher concentration of fluoride accelerated it. In all experiments, the pH was observed to rise to values higher than 8.0 units after 360 min of treatment.     

Simultaneous determination of nickel,iron, and copper in margarine by inductively coupled plasma-atomic emission spectroscopy after sample emulsification

Nickel, iron, and copper were determined in margarine samples by using emulsification followed by inductively coupled plasma-atomic emission spectroscopy. Sample treatment and instrumental conditions were optimized, and the results were compared with those obtained by a pseudodigestion method in order to evaluate the compatibility of both methodologies. The optimum amount of margarine in the emulsion was 35% when the surfactant Tween 80 was added as the emulsifier. Copper was below the detection limits of both methodologies, i.e., digestion and emulsion; iron and nickel concentrations found by both methodologies were similar. The detection limits of the emulsion method were 0.002, 0.015, and 0.092 mg/kg for copper, iron, and nickel, respectively. A benefit of the emulsion method is that laborious and lengthy sample digestion procedures are avoided. In addition, accurate and precise results are obtained. Recoveries with the emulsion method ranged from 101 to 104%, with relative standard deviations of < or = 6%.